This invention relates generally to a system that prevents keys from inadvertently being locked in a vehicle. More particularly this invention relates to an electronic system in which an alarm sounds and vehicle doors automatically unlock when the keys have been left anywhere inside the vehicle.
To the chagrin of automobile drivers, it is easy to lock ignition and door keys in a vehicle, thus locking the driver out. This occurs when the driver leaves the keys in the car, exits the car, and locks the doors without a key by manually manipulating the latch or electronically engaging the locks. While most drivers find this embarrassing and annoying, locking the keys in the car can also be dangerous if a small child or animal is locked inside.
For safety reasons, young children are often strapped into a safety seat for travel. It is likely that the child does not know how to unlatch the safety seat belts or is not dexterous enough to do it. Similarly such a child may not be able to unlock a car door from the inside, even if not strapped into a safety seat. If a driver inadvertently locks the car keys in the car while the child is inside, a precarious situation arises. The child can't get out and the driver can't get in.
As is often the case, drivers with small children may drive a van or station wagon. A common scene is to finish shopping and return to the car with groceries and a child. Before loading the groceries, the passenger compartment is unlocked with the keys and the child is placed in the car seat. The driver then goes to the trunk or rear of the van to load the groceries. The rear door is opened and because the driver wants to use two hands to load, the car keys are set down in the car. After the groceries are loaded, the driver slams the trunk or door tightly for security, locking the door by habit, only to realize in horror that the groceries, child and keys are now securely locked in the car.
A similar situation may arise if an animal is in the car when the driver exits the vehicle and inadvertently locks the keys in the car. Moreover, even if the driver leaves the doors unlocked, an active animal may inadvertently lock the doors by stepping on the door lock button or plunger, thereby locking itself in the car.
Aside from the embarrassment to the driver, and the subsequent expense and wasted time to call for police or a locksmith to unlock the door, the safety of the child or animal can become of great concern. If the vehicle is turned off, as is normally the case when keys are locked in the car, the interior environment of the vehicle is not controlled. In desert areas, the interior temperature of a closed vehicle can reach 140 degrees in a matter of minutes. Likewise in cold areas, the interior temperature can drop to sub-freezing temperatures in a very short time. These temperature extremes can be life-threatening to humans and animals locked in the car.
The prior art has endeavored to create devices which prevent car keys from being locked in a car, generally known as anti-lockout devices. However, these devices were not created to prevent life-threatening conditions to vehicle occupants. Instead they were developed to alert the driver that the ignition keys were still in the ignition upon the driver's exit and, if not retrieved, to disable the locking mechanisms. U.S. Pat. Nos. 4,709,777, 4,789,851, 4,428,024 and 4,419,712 describe variations on an electronic door lock interlock which senses the presence of a key in the ignition. When the key is in the ignition and the driver attempts to lock the doors, an alarm sounds and the locking mechanism is disabled. These devices work as anti-lockout devices only if the key has been left in the ignition. A driver would be locked out if the keys were left anywhere else in the car but the ignition, like the floor, on the seat, or in the trunk.
Instead of unlocking the car doors automatically when the keys have been left inside, other prior art inventions for keyless entry systems automatically lock the doors to prevent theft of the vehicle or its contents. These devices do not prevent or solve the situation where a child is locked in a car and, in fact, aggravate it. Keyless entry systems do not require keys to operate door locks, and use remote control technology to electronically operate door locks and the like. Instead of a key to insert in a mechanical lock, the driver carries a transmitter to signal the locks to engage electronically. Anti-lockout devices have been designed into this wireless technology so that if a transmitter is locked in the car, the driver may still enter with a key or by entering a preset code. For example, U.S. Pat. No. 4,672,375 describes a keyless entry system that alerts the driver if the transmitter has been left in the car. If the driver does not retrieve the transmitter, the doors automatically lock, the keyless entry system is disabled, and the car can be entered only with a key.
Anti-lock devices are well known in the prior art. However, until now, these devices served to alert the driver only if the key has been left in the ignition. If the keys are removed from the ignition, but still left somewhere in the car, the prior art devices are ineffective. Therefore, it is an object of this invention to overcome the problems of prior art and provide an anti-lockout system which will prevent the doors from locking if the keys have been left in the car, regardless of their location within the car. It is a further object of this invention to enable a driver to re-enter the car to retrieve the car keys if they have been left in the car. It is a further object of this invention to provide a system which will alert the driver that the keys have been left in the car so that the keys can be retrieved and the doors locked.